Temperature regulating system



Feb. 6, 1940. w MOGRATH 2,189,381

TEMPERATURE REGULATING SYSTEM Fi1ed.Jan. 13, 1936 5 Sheets-Sheet 2 7 Feb. 6, 1940. w, MCGRATH 2,189,381

TEMPERATURE REGULATING SYSTEM Filed Jan. 13, 1936 3 Sheets-Sheet 5 Patented Feb. 6, 1940 PATENT OFFICE TEMPERATURE BEGULATING SYSTEM William L. McGrath, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 13, 1936, Serial No. 58,867

11 Claims.

This invention relates to temperature regulat-' ing systems, and more particularly to that type of system for controlling the temperature of a. space.

Conventional heating systems using space thermostats of the on and ofl type for controlling a heater for heating a space, supply heat at a substantially full capacity to the space upon a call for heat by the space thermostat, and supply substantially no'heat to the space when the space thermostat is satisfied. Due to this intermittent supply of large amounts of heat to the space, and due to the inherent lag or inertia of such systems, overshooting and undershooting oithe space temperature is brought about.

It is known that by maintaining the temperature oi the heating medium at a predetermined value so as to supply just the correct amount of heat to the space to satisfy the heating load of the system, the space temperature may be maintained at a desired value. Specifically, it is known that upon an increase in the heating load the temperature of the heating medium may be increased to supply additional heat to the space to maintain the space temperature constant.

Conversely, upon a decrease in the heating load the temperature of the heating medium may be decreased to supply less heat to maintain the space temperature at the desired value.

It is the prime object of my invention. to provide a means for adjusting the temperature of the heating medium in accordance with the heating load on thesystem to maintain the space temperature at a desired value in such a manher as to prevent overshooting and undershooting oithe space temperature.

More specifically, it is an object of this invention to provide a means for intermittently adlusting the temperature of the heating medium in a step-by-step manner, whereby the temperature of the heating medium may be gradually brought to the desired value without causing the temperature thereof torise above the desired value or tolower below the desired value.

Still more specifically, it is an object of this invention to provide a condition responsive means ior maintaining the temperature of the heating medium at a desired value to supply suiiicient heat to a. space to maintain the space tempera- 50 ture at the desired value, along with means for raising in a step-by-step manner the setting of the condition responsive device to increase the temperature oi the heating medium in accordance with an increase in, the heating load and for lowering the setting 01 the condition responsive device for lowering the temperature of the heating medium in response to a decrease in the heating load;

The regulating system is so arranged that the adjustment of the setting of the condition 5 responsive means cannot be made faster than the recovery of the heating system to this adjustment or that the temperature of the heating fluid cannot increase or decrease faster than the rate of adjustment of the condition responl0 sive means. This mode of operation andthe manner in which it is accomplished also form objects of this invention.

It is another object of this invention toprovide means for adjusting a boiler thermostat 15 at one rate of speed when the space temperature deviates from normal it given amount and for adjusting the boiler thermostat at another rate of speed when the space temperature deviates from normal a greater amount in order to provide a normal, accurate temperature control of the space and to provide a rapid restoring of the temperature of the space to normal when the temperature of the space deviates a relatively great amount from normal.

Still another object of this invention is to provide a thermostat of novel construction which may be utilized in my invention.

Other objects and advantages will become apparent to those skilled in the art upon reference 30- to the accompanying specification, claims and drawings, in which drawings:

Figure 1 diagrammatically illustrates one form of my invention.

Figure 2 is a sectional view taken on the line 86 2-2 of Figure 1.

ure 3 is a diagrammatic illustration of another form of my invention. V

Figure 4 is a diagrammatic illustration of still another form of my invention, and

F gures 5 and 6 are detail 'views showing the. construction of a thermostat that may be utilized in the various modifications of my invention.

Referring now to Figure 1 of the drawings, a heating means for a space is illustrated at "I and this heating means is shown to comprise a boiler for purposes of illustration, although any other form of heating means may be utilized. The heating means I0 is shown to be heated by an oil burner ll, although any other type of firing means may be utilized. The oil burner II is controlled by a device responsive to the condition of the heating means l0 and may take the form of a boiler thermostat generally designated at l2, although this instrument may equally as well be a pressure responsive device. The setting of the boiler thermostat I2 is adjusted by means of an adjusting motor generally designated at l3, and this adjusting motor is in turn controlled by a space thermostat generally designated at l4.

The boiler thermostat l2 includes a housing l5 in which, is mounted an expansible bellows IS, the arrangement being. such that a pressure chamber is formed between the housing l5 and the bellows I6. This chamber is connected by means of a capillary tube I1 which in turn is connected to a bulb l8 located in intimate contact with the heating fluid of the heating means l0, and, as shown in the'drawings, it'is attached to the riser 20 leading from the heating means 4 [8 to the space 'to be heated. The bulb I8 is charged with a volatile fluid so that upon an'increase in temperature of the heating fluid the volatile fluid is vaporized to cause upward movement of a plunger 22 carried by the expansible bellows l6. l I

The plunger 22 is adapted to engage a lever 23 pivoted upon a knife edge 24 carried by a bracket 25. The bracket 25 may be secured by means of screw 26 to the casing 21 of the boiler thermostat. The lever 23 is provided with a projection 28 to which is secured one end of tension spring 28, the other end thereofbeing secured to a nut 30 which is mounted upon a screw 3|. The screw 3| is held against longitudinal movement by a collar 32 abutting against the upper surface of the casing 21. The tension spring 28 is adapted to rotate the lever 23 in a clockwise direction about the knife edge 24 and the plunger 22 is adapted to rotate the lever 23 about the knife edge 24 in a counter-clockwise direction upon an increase in the temperature of the heating.

fluid. A lug 33 overlying the knife edge 24 is provided on the lever 23 to maintain the parts in an assembled position. I

Plvotally mounted in the casing 21 of the boiler thermostat i2 is a mercury switch carrier clip 35 pivoted as at 35. The mercury switch carrier 35 carries mercury switches 31 and 38,-

the function of which will be pointed out more fully hereafter. The mercury switch carrier is provided with a slot 39 which is adapted slidably to receive a pin 40, the pin 40 being carried by an upwardly extending extension 4| of the pivoted lever 23. The arrangement is such that upon an increase in heating fluid temperature the mercury switch carrier is tilted in a clockwise direction and upon a decrease in temperature the mercury switch carrier is tilted in a counterclockwise direction. As is seen in Figure 1,. the mercury switch 31 is moved to a circuit making position upon a decrease in hating fluid temperature and to a circuit breaking position upon an increase in heating fluid temperature. The mercury switch 38 is so arranged that it makes contact when it is in a horizontal position or slightly on either side of the horizontal position and it is so arranged with respect to the mercury switch 31 that-it is in a circuit making position when the mercury switch 31 is at or near a horizontal position.

Referring now to Figure 2, it is seen that clockwise movement of the lever 23 is limited by an upper stop 43 and that counter-clockwise movement of the lever 23 is limited by means of a lower stop 44, the stops 43 and 44 being carried by a bracket 45 suitably mounted on the casing 21. A lever 46 is also pivoted on the bracket 45 as at 41, and carries a pivot 48 to which is secured a second lever 48. The second lever 48 is held in an adjusted positionwith respect to the first lever 46 by means of a screw 5|, the adjustment being permitted by the slot 50 in'the second lever 48. The second lever 48 is secured to one end of a tension spring 52, the other end thereof being secured to a nut 53 mounted on a screw 54 which is held against longitudinal movement by the screw head 55. The spring 53 therefore urges the lever 46 in a counter-clockwise direction. The lever 46 carries an abutment 56 which is adapted to engage the lower surface of the lever 23 and the lever 45 also carries an abutment 51 which is adapted to engage the undersurface of the lower stop 44.

"Assume that the parts are in a position wherein the lever 23 engages the lower stop 44 and therefore the mercury switches 31 and 38 are tilted in an extreme clockwise position. The mercury switches 31 and 38 will therefore be in circuit breaking positions. Upon a decrease in boiler temperature the springs 29 and 52 move the lever 23 in a clockwise direction away from the lower stop 44, and when this movement has been halfway completed the abutment 51 engages the lower stop 44 to prevent further actuation of the lever 23 by the spring 52. When the parts are moved to this position the switches 31 and 38 are movedto a substantially horizontal position wherein contact is established between the electrodes of the mercury switch 38 but wherein contact is not established between the electrodes of mercury switch 31 by reason of the angle of lag of the switch 31. Since the-spring 52 no longer actuates the lever.23, a greater temperature drop is required to allow the spring 23 to continue the clockwise movement of the lever 23 into engagement with the upper stop 43. When the lever 23 is moved into engagementwith the upper stop 43 the switches 31 and 38 are moved to an extreme counter-clockwise position wherein a circuit through the mercury switch 31 is established and the circuit through the mercury switch 38 is broken. Upon an increase in temperature the plunger22 is moved upwardly to move the lever 23 in a counter-clockwise direction against the tension of thespring 28 away from the upper stop 43. When the lever 23 has travelled substantially halfway, it engages the abutment 56 of the lever 46 and therefore further movement of the lever 23 is restrained by the spring 52. Movement of the lever 23 to this midposition causes movement of the mercury switches 31 and 38 to their horizontal positions,

whereby contact is established in the mercury I switch 38, and contact remains established in the mercury switch 31 by reason of the angle of lag of the mercury switch 31. .In order to move the lever 23 to its extreme counter-clockwise position the bellows l6 must not only overcome the a spring 28 but must also overcome the spring 52 operating through the lever 46 whereby an increased load is placed upon the bellows l6. When the temperature has risen sufllciently to overcome this increased load the lever 23 is &5

moved against the lower stop 44 and the mercury switches are moved to their extreme clockwise position to break the circuits established through the mercury switches 31 and 38. In this manner the differential of pressure required to move the lever 23 from the upper stop 43 to the lower stop 44, and vice versa, from the lower stop 43 to the upper stop 43, is increased and the amount of increase in differential may be ad- Justed by acliusting the tension of the spring 5:,

It is therefore seen that when the mercury switches 31 and 88 are moved to a substantially horizontal position, contact is established in the mercury switch 38 and contact may or may not be established in the mercury switch 31 depending upon which way the mercury switch 81 is moving.

The nut 38 associated with the tension spring 29 and the nut 53 associated with the tension spring 52 are provided with pointers 59 and 68 respectively, which extend outwardly through slots 6| and 62 respectively in the casing 21. Pointers 59 and 68 cooperate with indicia located on the casing 21 to indicate the tension in the springs 29 and 52 respectively in terms of temperature and also serve the purpose of holding the nuts 38 and 53 againstrotation so that rotary movement of the screws 3| and 54 causes longitudinal movement of the nuts 38 and 53 respectively. In this manner rotation of the screw 3| adjusts the temperature setting of the boiler thermostat and rotation of the screw 54 adjusts the differential of operation of the boiler thermostat.

In order to insure proper alignment of the boiler thermostat and therefore proper operation of the mercury switches 31 and 38, a. pendulum G4 is mounted in the casing 21 and is adapted to coact with a mark 85, whereby the instrument may be properly levelled.

The screw 3| for adjusting the temperature setting of the boiler thermostat I2 carries a bevelled gear 81 which meshes with another bevelled gear 68 which is driven through a reduction gear train 89 by motor rotors 18 and H upon energization of field windings 12 and 13. The various gears are suitably supported by a support 14 mounted on the casing 21. The arrangement is such that when the field winding 12 is energized the screw 3| is rotated to increase the tension in the spring 29, whereby the temperature setting of the boiler thermostat I2 is increased. Conversely, energization of field winding 13 causes reverse rotation of the screw 3| to decrease the tension in the spring 29, whereby the temperature setting of the boiler thermostat I2 is decreased.

Suitably mounted on the casing 21 is a bracket 16 which carries a strip of insulating material 11. Mounted upon the strip of insulating material 11 are contacts 18, 19, 88 and 8|, the contacts 18 and 19 being normally in engagement and the contacts 88 and 8| also being normally in engagement. Located between the contacts is an abutment 82 carried by a rod 83. Mounted on the rod 83 is a collar 84 which is engaged by a spring 85 to maintain the abutment 82 spaced midway between the contacts 18 and 8|. The rod 83 extends downwardly into the casing 21 and through an opening in the indicating arm 59. The rod 83 is screw threaded and is provided with spaced abutments' 86 and 81 which are adapted to be engaged by the indicating arm 59 at either extreme position thereof. The arrangement is such that when the temperature setting of the boiler thermostat I2 is raised to its maximum value the arm 59 engages the abutment 88 to move the abutment 82 into engagement with the contact 18 to break contact between the contacts 18 and 19. Likewise, when the tempera- 18, 19, 88 and 8| therefore form limit switches, the operation of which will be more fully pointed out hereafter.

The space thermostat, generally designated at I4, may comprise a bimetallic element 88 for carrying and operating a switch arm 98 which cooperates with spaced contacts III and 92. The arrangement is such that upon a decrease in space temperature the switch arm 98 is moved as indicated by the character C into engagement with the contact 9|, and upon an increase in space temperature the switch arm 98 is moved in the direction indicated by the character H into engagement with the contact 92.

A step-down transformer is generally designated at 94 and comprises a primary 95 suitably connected to a power source, not shown, and a secondary 96. One end of the secondary 98 is connected by a wire 91 to the bimetallic element 89 of the space thermostat I4. The contact 9| of the space thermostat I4 is connected by a wire 98 to the limit switch contact 19 and the associated limit switch contact 18 is connected by a wire 99 to one end of the field winding 12. The other end of the field winding 12 is connected by a wire I88 to one of the electrodes of the mercury switch 38. The other electrode of the mercury switch 38 is connected by a.- wire I8I to the other end of the secondary 98. The contact 92 of the space thermostat I4 is connected by wire I82 to the limit switch contact 88, and the associated limit switch contact 8| is connected by a wire I83 to one end of the field winding 13. The other end of the field winding 13 is connected to the junction of field winding 12 and the wire I88. A wire I85 leading from some source oi power, not shown, is connected to one of the elec trodes of the mercury switch 31 and the other electrode thereof is connected by wire I85 to the oil burner II. The oil burner II is in turn connected by a wire I81 to the source of power, not shown, the arrangement being such that when the mercury switch 31 is moved to a circuit making position a circuit is completed to cause operation of the oil burner II.

With the parts in the position shown in the drawings, the space temperature is at the desired value and consequently the switch arm 98 is midway between the contacts 9| and 92. The boiler thermostat is in such position as to maintain the mercury switch 31 in a circuit open position, whereby the oil burner II is non-opera.- tive. These positions result from the fact that the temperature of the heating fluid in the boiler I8 is at such a value as to supply the correct amount 0! heat to the space to maintain the space temperature at the desired value. Upon a decrease in boiler temperature the mercury switch 31 is moved to a circuit making position to cause operation of the oil burner II to restore the temperature of the heating fluid in the boiler I8 to the desired value. In this manner the oil burner II is intermittently operated to maintain the temperature of the boiler water at the desired value. The amount of operation of thaoil burner is determined by the setting of the differential adjusting means, and the temperature of the boiler water is determined by the setting of the boiler thermostat 2.

Upon an increase in the heating load which may be caused by an increase in heat loss from the space, the switch arm 98 of the thermostat I4 is moved into engagement with the contact 8| to complete a circuit from the secondary 88 through wire 01, bimetallic element a, switch "I ondary 96.

arm so, contact 9|, wire as, limit switch contacts I9 and I8, wire 99, field winding I2, wire I00, mercury switch 38, and wire IOI, back to the sec- This causes energization of the field winding I2 to increase the tension in the spring 29, whereby the temperature setting of the boiler thermostat I2 is increased. This increase in the tension of spring 29 causes movement of the mercury switch 31' to a circuit making position to cause energization of the oil burner II to cause heating of the heating fiuid in boiler I0. As the mercury switch 31 is moved to a circuit making raising of the setting of the boiler thermostat I2 is prevented. Due to the operation of the oil burner II the temperature of the boiler water is increased and when the temperature of the boiler water has increased suificiently, the mercury switch 31 is moved toward a horizontal position, the oil burner still being in operation, and the mercury switch 38 is moved to a circuit making position. This increase in boiler temperature supplies additional heat to the space to be heated, but if the space thermostat I4 is still calling for heat the above mentioned circuit through the field winding I2 is again completed to cause a further raising of the setting of the boiler thermostat I2. In this manner the setting of the boiler thermostat I2 is increased upon a call for heat by the space thermostat I4 in a step-bystep manner, until such time as the space thermostat shall become satisfied.

If the heating load should decrease, as caused by anincrease in outdoor temperature or by the congregation of a large number of people in the space, the space temperature will increase to move the switch arm 90 into engagement with the contact 92 to complete a circuit from the secondary 96 through wire 91, bimetallic element 89, switch arm 90, contact 92, wire I02, limit switch contacts 80 and 8|, wire I03, field winding I3, wire I00, mercury switch 38, and wire IOI, back to the secondary 96. Completion'of this circuit causes energlzation of the field winding I3 to decrease the tension of the spring 29, which lowers the setting of the boiler thermostat I2.

Decrease in the tension of the spring 29 in this manner causes clockwise movement of the mercury switch carrier to move the mercury switch 38 to a circuit breaking position, whereby fur.- ther downward adjustment of the boiler thermostat I2 is prevented. This decreasing of the tension in the sp ing 29 also moves the mercury switch 31 toward a circuit breaking position. When the temperature of the heating fluid in the boiler I0 decreases by reason of the oil burner II being de-energized, the mercury switch carrier 35 is moved in a counter-clockwise direction to move the mercury switches to a horizontal position, whereby mercury switch 38 is moved to a circuit making position but the mercury switch 31 remains in a circuit breaking position. If the space temperature is still above the desired value and the switch arm 80 is in engagement with the contact 90, the circuit through the field winding 13 is again reestablished to further decrease the tension in the spring 29 andfurther lower the setting of the boiler thermostat I2. The setting of theboiler thermostat {I2 will be continued to be lowered in this manner until such time as the space temperature is restored to normal and the switch arm 90 remains spaced midway between the contacts 8| and 92.

areaee such a value as to supply the correct amount of heat tothe space to maintain the space temperature constant, and that upon changes in the heating load either upwardly or downwardly the boiler thermostat is adjusted in a step-by-step manner, whereby accurate adjustment of the boiler thermostat is obtained and, overshooting, and undershooting of the space temperatureis prevented. By reason of the step-by-step action the adjustment of the boiler thermostat and the temperature of the boiler water are so interlocked that the boiler thermostat cannot be adjusted faster than the recovery of the heating system to this adjustment andthat the boiler water temperature cannot be changed faster than the rate of adjustment of the boiler thermostat.

The limit switches I8, 19, 80 and 8| located in series with the field windings I2 and I3 respectively, limit the adjustment. either upwardly or downwardly of the boiler thermostat I2 and these limits may be so selected that the boiler water temperature cannot rise above a predetermined value and cannot decrease below a predetermined lower value. It therefore follows that by reason of this construction the usual high limit switch is done away with and that a low limit control is provided.

Referring now to Figure 3, I have shown a modified form of my invention, which utilizes the same heating system, including the oil burner I I, the same boiler thermostat I2, the same adjusting motor I3, and a space thermostat I4. The boiler thermostat I2 is in all respects similar to the boiler thermostat of Figure l, with the exception that the mercury switch 38 is eliminated and the intermittent interruption of the adjusting motor is accomplished in a different manner, as will be pointed out more fully hereafter.

The space thermostat I4 of Figure 3 is shown to comprise a bimetallic element H0 suitably mounted on an adjusting lever III. The bimetallic element H0 carries three switch arms H2, H3 and H4. The switch arm H2 is adapted to engage spaced contacts H5 and H6. The switch arm H3 is adapted-to engage a contact H1, and the switch arm H4 is adapted to engage a contact H8. The contacts H1 and H8 are spaced apart farther than the contacts H5 and H8 so that greater temperature changes are required to make the contacts H1 and H8 than the contacts H5 and H6. The contacts H5 and H6 are used for the normal operation of the system. The

' functioning and operation of this thermostat will be pointed out more fully hereafter.

A wire I20 leading from a source of power, not shown, is connected to one end of a relay coil I2 I The other end of the relay coil I2I is connected by a wire I22 to oneof the electrodes of the mercury switch 31. The other electrode of the mercury switch 31 is connected by a wire I23 to the oil burner II, which in turn is connected by a wire I24 to the source of power, not shown. Therefore, when the mercury switch 31 is moved to a circuit making position the oil burner II is placed in operation and the relay coil I2I is energized. Although, the oil burner II and relay coil I2I are shown to be connected in series, they may equally as well be connected in parallel. When the relay coil I2I is energized a switch arm I25 is moved out of engagement with a contact' I28 and a switch arm I2'I is moved into engagement with a contact I28. When the relay coil III is dcenergized by reason of the movement .I21 being accomplished by means of springs or gravity or other means, not shown.

Since the boiler thermostat I2 of Figure 3 is in all respects the same as that of Figure 2, it is seen that the oil burner II is intermittently operated to maintain the boiler water temperature at the desired value to supply the correct amount of heat to the space to be heated. Upon a decrease in space temperature as caused by an increase in the heating load the switch arm H2 is moved in the direction indicated by the character C into engagementwith the contact II! to complete a circuit from the secondary 66 through wire I36, bimetallic element II6, switch arm II2, contact IIS, wire I3I, switch arm I26, contact I26, wires I32 and I33, limit switch contacts 16 and 16, wire I36, field winding. 12 and wire I36, back to the secondary 66 providing the oil burner II is oil. This causes energization of the field winding 12 to increase the tension in the spring 26 to raise the setting of the boiler thermostat I2. This causes movement of the mercury switch 61 to a circuit making position to cause operation of the oil burner II and energization of the re,- lay coil I2I. Energization of the relay coil I2I moves a switch arm I25 out of engagement with the contact I26 to break the circuit through the field winding 12, whereby the upward adjustment of the boiler thermostat I2 is interrupted. Due to the operation 01' the oil burner II the temperature of the heating fluid is increased. Due to this increase in boiler water temperature the mercury switch 31 is moved to a circuit breaking position and the oil burner I I is de-energized and the relay coil I2I is likewise de-energized. If the space temperature is not restored to normal at this time and the switch arm H2 is still in engagement with the contact II5, the circuit through the field winding 12 is re-establ ished to further increase the setting of the boiler thermostat I2. This mode of operation is repeated until such time as the space thermostat is satisfied.

If the space temperatureshould rise above the normal value, as caused by a decrease in the heating load, the switch arm H2 is moved into,

engagement with the contact II6. When the boiler thermostat moves the mercury switch 31 to a circuit making. position in an effort to maintain the boiler water temperature at the desired value the relay coil I2I is energized to move the switch arm I21 into engagement with the contact I26. This causes completion of a circuit from the secondary 66 through wire I36, bimetallic element I I6, switch arm II2, contact II6, wire I36, switch arm I21, contact I26, wires I31 and I36, limit switch contacts 66 and II. wire I36, field winding 13 and wire I35, back to the secondary 66 providing the oil burner II is on. This causes energization of the field winding 13 to decrease the tension in the spring 26 and consequently lower the setting oi the boiler thermostat I 2. This causes movement of the mercury switch 31 to a circuit breaking position to stop operation of the oil burner II and to deenergize the relay coil I2I, whereby the circuit through the field winding 13 is broken and the downward adjustment of the boiler thermostat I2 is interrupted. When the boiler water temperature decreases so as to move the switch arm 31 into circuit making position, which causes operation of the oil burner II and movement of the switch arm I21 into engagement with the contact I26, ii the switch arm I I2 of the space thermostat I 6 is still in engagement with the contact II 6 the circuit through the field winding 13 is again established to again lower the setting of the boiler thermostat I2. This latter mode of operation will continue until'such time as the space temperature is restored to the normal value.

From the above it isseen that in this modification as in the previous modification I have provided a boiler thermostat for controlling the operation of the boiler, which boiler thermostat is adjusted in a step-by-step manner for maintaining the space temperature at the desired value regardless of changes in the heating load.

The adjustment of the boiler thermostat is so arranged in this modification that when the setting of the boiler thermostat is being raised to increase the boiler water temperature, the operation of the oil burner is intermittently interrupted and when being lowered to decrease the temperature of the boiler water, the oil burner is intermittently operated. These intermittent operations and interruptions have the effect of cushioning the raising or lowering of the boiler water temperature to prevent overshooting" or undershooting of the space temperature. Therefore, in this modification as in the previous modification an interlocking action is established between the rate of temperature change in the boiler water and the rate of adjustment of the boiler thermostat so that neither will be changed more rapidly than the other.

If there should be a sudden change in the heating load of a substantial extent so as to alter the space temperature sumciently to move the switch arm, II3 into engagement with the contact II! or to move the switch arm III into engagement with the contact II6, depending upon whether the space temperature increases .or decreases, the adjusting motor I3 is energized secondary 66. Completion of this circuit causes energization of the field winding 12 to raise the setting 01 the boiler thermostat, andsince this circuit shunts the switch arm I26 and the contact I26, the boiler thermostat is freely ad- Justed in an upward direction to rapidly change the setting of the boiler thermostat whereby the boiler. water temperature may be rapidly increased to quickly restore the space temperature to the desired value.

Likewise, upon a sudden and large decrease in the heating load so as to cause movement of the switch arm I into engagement with the contact I I6 a circuit is completed from the secondary 66 through wire I36, bimetallic IIII, switch arm Ill, contact II6, wires I62 and I36, limit switch contacts 66 and 6|, wire I36, field winding 13, and wire I36, back to the secondary 66. Completion of this circuit causes energization of the field winding 13, and since this circuit shunts the switch am: I21 and the contact I26, the boiler thermostat I2 is adjusted downwardly in intermittently adjusting a boiler thermostat in a step-by-step manner for maintaining a desired temperature value within a space, but have also provided means for rapidly adjusting a boiler thermostat to quickly restore the space temperature to the desired value.

Referring now to Figure 4, I have shown an arrangement somewhat similar to that shown in Figure 3 for accomplishing substantially the same results, wherein there are utilized a boiler thermostat I2, an adjusting motor I3, a space thermostat I4, and a relay which are similar to those disclosed in Figure 3. The relay of Figure 4 is shown to com-prise'a relay coil I44 for operating switch arms I and I46, the arrangement being such that upon energization of the relay coil I44 the switch arm I45 is moved into engagement with a contact I41 and the switch arm I46 is. moved out oi! engagement with a contact I48.

Upon deenergization of the relay coil I44 the switch arm I45 is moved out of engagement with the contact I41 and the switch arm I46 is moved into engagement with the contact I48. A wire I49 leading from some source of power, not shown, is connected to one end of the relay coil I44 and the other end is connected by a wire I50 to one of the electrodes of the mercury switch 31. The other end, of the mercury switch 31 is connectedby wire I5I to the oil burner II which in turn is connected by wire I52 to the source of power. Therefore, when the mercury switch 31 is moved to a circuit making position the oil burner II is placed in operation and the relay coil I44 is energized. The burner II and the relay coil I44 may equally as well be connectedin parallel.

The space thermostat I4 utilized in this modiflcatlon is illustrated in detail in Figures 5 and 6 and may comprise a bimetallic element I54 mounted upon a post I55 and carrying a blade I56. The blade I56 is split longitudinally to term two blades I51 and I58, blade I51 carrying contacts I59 and'I60 and blade I58 carrying contacts I6I" and I62. Upon a decrease in space temperature the 'blade' I56 is moved in the direction indicated by thecharaoter C and the contact I59 is moved into engagement with a contact I63, and upon a further decrease in space temperature the contact IN is moved into engagement with a contact. I65, this additional movement being permitted by the flexibility or the blade I56. Likewise, .upon .an increase in space temperature the contact I60 ismoved into engagement with a. contact I64, and. upon a further increasefin space temperaturethe coni'zzgt I62 is movedintoengagement with a contact 1 As in theprevious modifications, the boiler thermostat operates the mercury switch 81 to operate the oil burner II to'maintain the temperature of the boiIer water at the desired value to supply the. correct amount of heat to the space to maintain the space temperature at the desired value. Upon a decrease in space temload, the contact I58 is moved into engagement with the contact I12.

with the contact I63 to complete a circuit from the secondary 96 through wire I69, bimetallic element I54 blade I56, contact I59, contact I68,

wire I10, a bimetallic element I1I, a contact I12 interrupted by means of the switch arm I46,

breaking engagement with the contact H8 in the manner pointed out with respect to Figure 3. The raising of the setting of the boiler thermostat is further interrupted by means of the thermo-electric mechanism. comprising the bi---';

metallic element I1I, the contact I12 and'the heater I13. This interruption is caused by energization of the heater I19 which causes flexing of the bimetallic element I1I out of engagement In this manner the adjustment of the boiler thermostat is materially retarded.

If the space temperature should increase so as to move the contact I60 into engagement with the contact I64 a circuit is completed from the secondary 96 through wire I68, bimetallic element I54, blade I56, contacts I60 and I64, wire I19, bimetallic element I80, contact I8I, heater I82, wires I83 and I84, switch arm I45, contact I41, wire I85, limit switch contacts 80 and 8 I, wire I86, field winding19 and wire I18, back to the secondary 96. Completion of this circuit causes energization of the field winding 18 to lower the setting of the boiler thermostat l2. The lowering of the setting of the boiler thermostat I2 is interrupted by the action of the switch arm I45 in the mannerpointed out with respect to Figure 3. The lowering of the setting of the boiler thermostatis additionally retarded by the action of the'thermo-electric mechanism comprising the bimetallic arm I60, the contact I8I and the heater I82. In this manner the rate of adjustment of the boiler thermostat I2 in a downward direction is likewise materially retarded.

If the space temperature should drop sumciently far so as to cause engagement of the? 50 contacts I6Iand I65, a shunt circuit is completed the novel features of one modification may be incorporated with the novelie'atures of another modification to accomplish desired results. Specifically, the means for rapidly adjusting the boiler temperature of Figures 3 and 4 upon a predetermined'deviation of-space temperature may be equallyapplied' to Figure 1, and such a modiflcation of Figure 1 is within the contemplation of this invention. The interrupting means comprising the theme-electric devices of Fi ure 4 disclosed various forms of my invention, other likewise may equally as well be provided in the modification shown by Figures 1 and 3.

From the above description 01 the various modifications of my invention it is seen that the oil burner is intermittently interrupted when the boiler water temperature is being increased in Figures 3 and 4, and is intermittently placed in operation when the boiler water temperature is being decreased in Figures 3 and 4. This may not be the case in the modification shown in Figure 1, since the oil burner may remain in operation during upward adjustment of the boiler thermostat or may remain out of operation during downward adjustment of the boiler thermostat. If it be desired to have the operation of the oil burner interrupted upon upward adjustment of the thermostat and intermittently operated upon downward adjustment of the boiler thermostat in Figure 1, a diflerent typeof mercury switch may be substituted for the mercury switch 38 of Figure 1. This mercury switch could comprise a pair of electrodes located in each end of the mercury switch, one of the pair of electrodes being adapted to be made when the mercury switch 31 is tilted to a circuit making position to place the oil burner in operation and the other pair of electrodes may be made when the mercury switch 31 is tilted to a position to stop operation of the oil burner. These pairs of electrodes respectively may function the same as the switch arm I21 and contact I28, and the switch arm I25 and contact I 26, of Figure 3, and these pairs of electrodes may be connectedto the field winding 12 and 13 of the adjusting motor I3 in the manner disclosed in Figure 3.. This would give identical operation to that disclosed in Figures 3 and 4 and cause intermittent operation of the oil burner as the setting of the boiler thermostat is being raised, and cause intermittent operation' of the oil burner as the setting of the boiler thermostat is being lowered.

From the above it is seen that I have provided a temperature control system wherein a condition responsive means, described as a boiler thermostat, is adjusted in a step-by-step manner in accordance with changes in the heating load toadjust the temperature of the heating means, described as a hot water boiler, to supply the correct amount 01' heat to the space to maintain the space temperature at the desired value regardless of changes in the heating load. In all instances the adjustment of the condition responsive means is interlocked wlth respect to the temperature of the heating fluid, so that the temperature 01 the heating fluid may not be changed faster than the adjustment of the condition responsive means, or that the condition responsive means may not be adjusted faster than the change in the temperature of the heating fluid. As pointed out above, the operation of the oil burner may be intermittently interrupted upon a raising of the adjustment of the condition responsive means, and the oil burner may be intermittently operated upon a lowering oi the setting of the condition responsive means to provide a cushioning effect whereby "overshooting and undershooting of the space temperature is prevented. Also by reason of my invention, provision is made for slowly adjusting the boiler thermostat when the temperature of the space deviates only slightly from normal and for rapidly adjusting the boiler thermostat when the temperature deviates a greater amount from normal.

Although for purposes of illustration I have forms thereof may become apparent to those skilled in the art, and consequently this invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In a system of the-class described, the combination of heating means for a space, means responsive to the condition of the heating means for controlling said heating means, means responsive to space temperatures for adjusting said condition responsive means, and means responsive to the action of said condition responsive means for controlling the adjustment of said condition responsive means by said space temperatu e responsive means. A

2. In a system of the class described, the combination of heating means for a space, means responsive to the condition of the heating means for controlling the heating means to maintain the condition of the heating means at given values, means responsive to the load on the heating system for adjusting the setting of the condition responsive means to maintain the condition of the heating means at a value which will supply the correct amount of heat to the space and maintain the space temperature at the desired value, and means responsive to the operation of the heating means for controlling the adjustment of the condition responsive means.

3. In a system of the class described, the combination of heating means for a space, means responsive to the condition of the heating means for intermittently energizing the heating means to maintain the condition of the heating means at given values, means responsive to space temperatures for adjusting the setting of the condition responsive means to maintain the condition of the heating means at a value which will supply the correct amount of heat to the space to maintain the space temperature at the desired value, and means operative upon energization of the heating means for interrupting the adjustment of said condition responsive means by said space temperature responsive means.

4. In a system of the class described. the combination of heating means for supplying heating fluid to a space, means responsive to the condition of the heating fluid for controlling said heating means, means responsive to space temperatures for adjusting said condition responsive means, means operative upon slight deviation in space temperature for controlling the adjustment of said condition responsive means by said space temperature responsive means, and means for preventing operation of said last mentioned controlling means when the space temperature deviates from normal a substantial amount.

5. In a system of the class described, the combination of heating means for a space, means responsive to the condition of the heating means for controlling the heating means to maintain the condition of the heating means at given values, means responsive to the load on the heating system for adjusting the setting of the condition responsive means to maintain the condition of the heating means at a value which will supply the correct amount of heat to the space and maintain the space temperature at the desired 70 value, and means responsive to predetermined changes in the value of the condition of the heating means for controlling the adiustment of the condition responsive means when the load on the heating system changes a given amount but per- ,and maintain the space temperature at the desired value, and means responsive to the operation of the heating means for retarding the adjustment of the condition responsive means when the load on the heating system changes a given amount but permitting free adjustment when the load on the heating system changes a greater amount.

7. In a system of the class described, the combination of heating means for supplying heating fluid to a space, means responsive to the condition of the heating fluid for controlling the heating means, means responsive to predetermined 7' bination of heating means for a space, electrically changes in space temperature for adjusting said condition responsive means at one rate, and means responsive to predetermined greater changes in space temperature for adjusting said condition responsive means at another rate.

8. In a system of the class described, the combination of heating means for a space, electrically operated firing means for said heating means, means responsive to the condition of said heating means, switching means operated by said conditionresponsive means, electrical connections between said switching means and said firing means, a space thermostat, adjusting means for said condition responsive means, electrical connections between said thermostat and said adjusting means, and switching mechanism operated by said condition responsive means in said last mentioned electrical connections to retard the adjustment of said condition responsive means.

9. In a system of the class described, the comoperated firing means for said heating means, means responsive to the condition of said heating means, switching means operated by said condition responsive means, electrical connections between said switching means and said firing means, a space thermostat, adjusting means for said condition responsive means, electrical connections between said thermostat and said adjusting means, a relay coil in said first mentioned electrical connections, and switching mechanism in said second mentioned'electrical connections operated by said relay coil for retarding the adjustment of said condition responsive means.

l0. In a system of the class described, the combination of heating means for a space, electrically operated firing means for said heating means,

' means responsive to the condition of said heating means, switching means operated by said condition responsive means, electrical connections between said switching means and said firing} means, a space thermostat, adjusting means for said condition responsive'means, electrical connections between said. thermostat and said adjusting means, switching mechanism in said last -mentioned electrical connections to retard the adjustment of said condition responsive means, and other electrical connections between said thermostat and said adjusting means adapted to shunt said last mentioned switching mechanism.

11. In a system of the class described, the combination of heating means for a space, electrical- 

